The fabrication of photomasks may require optical inspection of top and bottom side of the photomask. Common optical inspection devices to the contrary are configured for single side inspection at an inspection site provided on top of an X-Y stage. This requires a top and bottom side flipping of the photomask between consecutive top and bottom side inspection. To keep time intervals for transfer and top and bottom side flipping to a minimum, there exists a need for a photomask flipper with a minimal footprint to be operated within an immediate vicinity of the inspection site. The present invention addresses this need.
Photomasks are commonly handled within an enclosed environment of the optical inspection device by a robotic arm that transfers the photomasks at least between an external access port and the inspection site. In case of an employed photomask flipper, the robotic arm may transfer the photomasks between the external access port, the flipper and the inspection site. To keep the space requirement for the robotic arm to a minimum, there exists a need for a photomask flipper that may be loaded and unloaded along a single transfer axis and within a single loading plane. The present invention addresses also this need.
Photomasks are commonly transported in well known containers within which they may be stacked in arbitrary initial supply orientation. But to perform optical inspection it is commonly required that the photomask is positioned in a predetermined orientation. Therefore, there exists a need for photomask flipper and system that identifies an arbitrary initial spatial photomask orientation and that automatically spatially reorients the photomask into a predetermined final spatial orientation. The present invention addresses also this need.
Optical inspection devices are desirably configured with a minimum footprint while providing a highly automated functionality. Particularly, automated transfer of the photomasks needs to be provided with a highly compact robotic arm limited to in plane photomask handling. Therefore, there exists a need for a photomask flipper that provides also lifting from and lowering onto the robotic arm of the photomask. The present invention addresses this need.
Photomasks are increasingly configured with well known pellicles. The presence of a pellicle may be initially unknown but may need to be automatically detected such that optical inspection may be eventually automatically adjusted for through-pellicle measurements. The present invention addresses also this need.